表面粗糙度对304不锈钢早期点蚀行为影响的电化学方法

采用动电位扫描、电化学阻抗谱和电化学噪声等方法研究了4种不同表面粗糙度304不锈钢电极在质量分数为3％的NaCl溶液中的早期腐蚀行为.随着不锈钢电极表面粗糙度的下降,304不锈钢自腐蚀电位与点蚀电位均有所上升;电荷转移电阻噪声电阻明显升高,而电位标准偏差与电流标准偏差则有所降低;粗糙度0.25μm的电极在阻抗谱低频区出...     

304NG奥氏体不锈钢在超临界水环境中的腐蚀行为

采用腐蚀增重法研究了304NG奥氏体不锈钢在550~650℃/25 MPa的超临界水(SCW)中的腐蚀行为。使用SEM和EDS分析了材料的氧化动力学、氧化膜表面形貌、氧化膜截面形貌和合金元素分布。结果表明:304NG奥氏体不锈钢在SCW中的腐蚀增重服从抛物线生长规律;在550℃的SCW中具有较好的抗腐蚀性能,当温度升高到650℃时,腐蚀增重速率急剧升高;304NG奥氏体不锈钢在SCW中腐蚀初期形成薄而致密的氧化膜,之后则会出现疖状腐蚀,并且腐蚀岛的尺寸随着腐蚀时间的延长而逐渐增大,650℃时尤为明显;腐蚀生成的氧化膜形态为典型的双层结构。     

重力对304不锈钢点蚀行为的影响

采用恒电位极化法、电化学阻抗谱和三维视频显微镜研究了304不锈钢在3.5％ NaCl溶液中水平放置和垂直放置时的点蚀行为.结果表明,试样垂直放置比水平放置更易达到稳定点腐蚀,由于重力作用使垂直放置的蚀孔内腐蚀产物更易扩散到孔外,加速点蚀的诱发和亚稳态点蚀向稳态点蚀的转变.阻抗谱等效电路中元件参数的分析结果表明,垂直放置的试样表面局部腐蚀比水平放置的更严重.     

304L/ER316L奥氏体不锈钢焊接板的点蚀行为

采用三氯化铁浸泡试验和电化学试验研究了核电站乏燃料池覆面用304L/ER316L/304L奥氏体不锈钢焊接板在3.5%(质量分数)NaCl溶液(溶液1),含2700mg/L B3+的纯硼酸溶液(溶液2)和含2700mg/L B3++200mg/L Cl-的混合溶液(溶液3)中的点蚀行为,同时研究了温度和氯离子对其点蚀行为的影响。结果表明:在三种溶液环境中,焊接板不同区域的耐点蚀性能由强到弱依次为焊缝区>母材区>热影响区。焊缝金属耐点蚀性能最优的主要原因是Ni、Mo含量较高,而热影响区的最差是由于显微组织不良。在30,40,60℃溶液2中,即使在高电位下也未观测到焊接板发生明显点蚀,而掺杂200mg/L Cl-后,焊接板的点蚀倾向显著增加,点蚀敏感性随温度升高而升高。符合设计参数的纯硼酸溶液是很好的服役环境,但当其中加入Cl-后,焊接板的耐点蚀性能会大幅降低,故乏燃料池在服役期间,应严格控制水温变化并监控水质,避免温度长时间过高及侵蚀性Cl-含量超标。     

The Effect of Surface Roughness on the Corrosion Properties of Type AISI 304 Stainless Steel in Diluted NaCl and Urban Rain Solution

Due to their good corrosion resistance, favorable mechanical properties, and reasonable price regarding their excellent properties, austenitic stainless steels have, over recent decades, become one of the alloys that are increasingly used in civil engineering and building, as well as for specific architectural purposes. Architects often design stainless steel exterior elements with higher surface roughnesses, which are not resistant to corrosion processes. The aim of this work was to investigate the influence of different types of surface finishes to stainless steel of quality AISI 304 on the corrosion properties of this steel. In order to achieve this goal, electrochemical tests were performed on different surface finishes in two different environments: in an NaCl aqueous solution, and in simulated urban rain which contained no chlorides. In addition to the electrochemical methods used, surface roughness was also measured, and XPS surface analyses were performed. The results of the investigation showed that surface roughness affects the growth of the passive layer in urban rain significantly; however, the growth of such a film is retarded in the case of the NaCl aqueous solution. Based on the results of the performed analyses, it was found that, in the NaCl solution, the pitting potential depended strongly upon the surface roughness and the surface finish, but this was not true for the samples tested in urban rain.     

304不锈钢在硝酸环境中的腐蚀电化学行为

采用极化曲线和电化学阻抗谱研究了硝酸温度和含量对304不锈钢耐蚀性能的影响。结果表明,在钝化电位下,304不锈钢在硝酸溶液中的阻抗呈现容抗特征,阻抗值达到104Ω·cm2,形成的钝化膜致密完整,随着温度的升高,阻抗值和相位角都减小,局部腐蚀加剧。高温和高含量均会促进钝化膜的溶解,进而加速304不锈钢在硝酸中的腐蚀。     

温度对904L不锈钢耐点蚀性能的影响

采用FeCl3溶液浸泡试验、动电位极化、电化学阻抗谱及体式显微镜研究了904L超级奥氏体不锈钢在不同温度下的点蚀行为。结果表明:溶液温度为25℃时,904L不锈钢具有优异的耐点蚀性能,随着溶液温度的升高,其耐点蚀性能下降,在65℃FeCl3溶液中基体表面产生严重的点蚀坑。在不同温度模拟海水溶液中的电化学测试结果同样表明:随着试验温度的提高,自腐蚀电流密度增大,点蚀电位下降,点蚀敏感性提高;EIS均为单一的容抗弧,温度升高,容抗弧半径减小,材料腐蚀速率增大,耐蚀性降低。     

纳米孪晶强化304奥氏体不锈钢的应变控制疲劳行为

利用动态塑性变形工艺制备块体纳米孪晶强化304奥氏体不锈钢样品并研究其低周疲劳行为。应变控制疲劳测试发现,包含30%(体积分数)纳米孪晶结构的304奥氏体不锈钢具有优异的低周疲劳寿命和高循环应力水平,同时循环软化程度随应变幅增加而减弱,与传统纳米结构金属材料"应变幅愈高,软化程度愈明显"的趋势截然不同。优异的低周疲劳性能主要得益于高强度纳米孪晶晶粒优异的结构稳定性以及其与相邻再结晶晶粒协同塑性变形,有效抑制应变局域化和疲劳裂纹萌生。     

时效对304不锈钢晶间腐蚀行为的影响

对304不锈钢进行时效处理,利用EPR(电化学动电位再活化法)对时效处理后的试样进行腐蚀试验,通过金相显微镜观察不锈钢微观形貌。结果表明,未经敏化处理的304不锈钢不会有晶间腐蚀的产生,700℃敏化后,在400~500℃时效温度下,随着时效温度的升高,晶间腐蚀敏感性也随之增大。因此,应严格控制304不锈钢的焊接工艺参数,杜绝晶间腐蚀的产生。     

Corrosion Resistance of PAPVD TiN Coating on AISI 304 Stainless Steel

In this work the corrosion resistance of PAPVD TiN hard coatings on AISI 304 stainless steel with a titanium interlayer has been addressed. Cyclic voltammetry corrosion tests in NaCl 3.5% solutions were performed for samples prepared by depositing TiN/Ti onto steel using different deposition parameters. The surface morphology of the samples was examined by using a scanning electron microscope (SEM) and phase analysis was performed by X-ray diffraction (XRD). The cyclic voltammetry curves showed two distinct behaviours. Firstly, a reduction in corrosion resistance was observed when current density was increased for the whole potential range studied. The second observation, no less important, was the increase in corrosion resistance compared to the uncoated steel. The TiN films deposited showing (III) preferred orientation showed better corrosion resistance than films presenting other orientations.     

不锈钢在NaCl溶液中点蚀的数值模拟

基于格子玻尔兹曼(LB)方法,为模拟多相多组分流动与传输、电化学反应、固液相间转化等,建了不锈钢点蚀的LB腐蚀模型。应用该模型,得到了不锈钢在点蚀全过程中点蚀坑形貌特征变化以及不同组分的含量分布情况。该模型能够清晰地说明不锈钢点蚀的反应机理,包括点蚀成核、点蚀的亚稳态过程以及点蚀的稳态过程。对比模拟结果同试验结果可以发现,腐蚀量随时间变化的趋势大致相同,这证明了该模拟方法的准确性。     

Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.     

Corrosion Resistance of Friction Surfaced AISI 304 Stainless Steel Coatings

Corrosion resistance of friction surfaced AISI 304 coating in boiling nitric acid and chloride containing environments was found to be similar to that of its consumable rod counterpart. This was in contrast to the autogenous fusion zone of GTAW weld which showed inferior corrosion resistance with respect to the consumable rod. The superior corrosion resistance of friction surfaced coatings was attributed to the absence of δ-ferrite in it.     

AISI304不锈钢钝化膜在电解质溶液中腐蚀时的半导体性质

应用电位-电容测试和Mott-Schottky分析技术研究了AISI304不锈钢钝化膜在电解质溶液中的半导体性质.结果表明,不锈钢钝化膜在氢氧化钠溶液中,随着浸泡时间延长,半导体类型转变电位发生负移;在硫酸、硫酸钠两种溶液中转变电位无明显变化.随着腐蚀时间的延长,溶液中不锈钢钝化膜的载流子密度逐渐增加,其载流子密度在几种溶液中从小到大的顺序依次为硫酸钠,氢氧化钠,硫酸.不锈钢在三种溶液中的Mott-Schottky曲线均出现频率分化,其原因可能为钝化膜中载流子的产生-复合存在时间效应;在氢氧化钠溶液中,钝化膜腐蚀的主要原因为富铬层导电能力增强;在硫酸、硫酸钠两种溶液中,钝化膜腐蚀的主要原因为富铁层导电能力的增强.     

304不锈钢点蚀行为的电化学噪声研究

本文利用电化学噪声技术检测了304不锈钢在6．0％（质量分数）FeCl3溶液中的点蚀行为。通过电化学噪声的时、频域分析和电化学噪声信号的统计分析以及相应的腐蚀形貌,研究了蚀点的生长过程。结果表明,浸泡初期噪声电阻Rn在较高水平波动,试样处于钝化状态;浸泡4～14h为点蚀诱导期,Rn开始降低,峭度和不对称度增大,出现明显的噪声峰,试样表面业稳态点蚀形核,生成的亚稳态点再钝化,通过扫描电镜观察未发现蚀点;浸泡14～32h为亚稳态点蚀向稳态点蚀过渡期;浸泡22h后,观察到电位噪声突然下降后不再恢复,功率密度（PSD）图低频区出现白噪声水平,亚稳态蚀点发展成为稳态的蚀点,通过扫描电镜观察到小而浅的蚀点;浸泡32～48h后材料处于稳定的点蚀阶段,通过扫描电镜观察到口径较大且较深的蚀点。     

Comparison of Roller Burnishing Method with Other Hole Surface Finishing Processes Applied on AISI 304 Austenitic Stainless Steel

Component surface quality and selection of the optimum material are the main factors determining the performance of components used in machine manufacturing. The level of hole surface quality can be evaluated by the measurements regarding surface roughness, micro-hardness, and cylindricity. In this study, data had been obtained for different hole drilling methods. The characteristics of materials obtained after applications were compared for different hole-finishing processes to identify best hole drilling method. AISI 304 austenitic stainless steel material was used. Surface finishing of holes were performed using drilling, turning, reaming, grinding, honing, and roller burnishing methods. The results of the study show that the roller burnishing method gives the best results for mechanical, metallurgical properties, and hole surface quality of the material. On the other hand, the worst characteristics were obtained in the drilling method.     

Studies on Stress Corrosion Cracking of Super 304H Austenitic Stainless Steel

Stress corrosion cracking (SCC) is a common mode of failure encountered in boiler components especially in austenitic stainless steel tubes at high temperature and in chloride-rich water environment. Recently, a new type of austenitic stainless steels called Super304H stainless steel, containing 3% copper is being adopted for super critical boiler applications. The SCC behavior of this Super 304H stainless steel has not been widely reported in the literature. Many researchers have studied the SCC behavior of steels as per various standards. Among them, the ASTM standard G36 has been widely used for evaluation of SCC behavior of stainless steels. In this present work, the SCC behavior of austenitic Fe-Cr-Mn-Cu-N stainless steel, subjected to chloride environments at varying strain conditions as per ASTM standard G36 has been studied. The environments employed boiling solution of 45 wt.% of MgCl₂ at 155 °C, for various strain conditions. The study reveals that the crack width increases with increase in strain level in Super 304H stainless steels.     

Effect of Boron Added Corrosion Behavior of Cast 304 Stainless Steel

Protection of Metals and Physical Chemistry of Surfaces - Seven groups of the cast 304 stainless steels with boron addition as 0, 10, 20, 30, 40, 50, and 60 ppm were used to investigate their...     

AISI304奥氏体不锈钢低温离子渗碳工艺优化研究

用正交实验法研究了AISI304奥氏体不锈钢低温离子渗碳工艺。结果表明,优化后的奥氏体不锈钢低温离子渗碳工艺参数为渗碳温度500℃、C3H8：H2=1：30、氩气流量20ml／min、渗碳时间6h。用优化工艺参数处理的奥氏体不锈钢表面可获得单一的Sc相组织,硬度高达780HV0．05。     

304 不锈钢在氯化钠介质中点蚀缓蚀剂的研究

目的研究钼酸钠、葡萄糖酸钠及其复配物在氯化钠介质中,对304不锈钢点蚀的缓蚀作用。方法对钼酸钠、葡萄糖酸钠按不同配比进行复配得到不同缓蚀剂,采用极化曲线法分别测试在这几种缓蚀剂存在的条件下,304不锈钢在3.5%(质量分数,后同)NaCl溶液中的点蚀电位。结果单组分的钼酸钠、葡萄糖酸钠对在3.5%NaCl介质中的304不锈钢点蚀有一定的抑制作用,且两种缓蚀剂有明显的协同缓蚀效应。结论当复配缓蚀剂配比为c(钼酸钠)∶c(葡萄糖酸钠)=2∶1时,其缓蚀效果达到最佳,点蚀电位为436 mV。